chendeben/MailSend @ feature/webhooks

chendeben 2d0d2118bd docs: pin webhook payload transaction and attempt counting		1 mesiac pred
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2026-07-09-mailhub-ui-redesign-design.md	037217ed2a docs: clarify UI redesign dual entries and dashboard metrics	1 mesiac pred
2026-07-09-mailhub-webhooks-design.md	2d0d2118bd docs: pin webhook payload transaction and attempt counting	1 mesiac pred